Electronic musical instrument with fluid pressure actuated volume control



May 10, 1966 JENNY 3,250,843

ELECTRONIC MUSICAL INSTRUMENT WITH FLUID PRESSURE ACTUATED VOLUMECONTROL Filed Aug. 19, 1964 3 Sheets-Sheet l Filfer|-1 OscillafionGenerator Georges Jenny IN V EN TOR.

AGENT May 10, 1966 G. JENNY 3,250,843

ELECTRONIC MUSICAL INSTRUMENT WITH FLUID PRESSURE AGTUATED VOLUMECONTROL Filed Aug. L9, 1964 C5 Sheets-Sheet 2 A A A L 3 i 48 ,4 HIVariable Resisfance /9 7 a o I 50 I I f H is I Y l 2 I \V I 4 I GeorgesJenny IN V EN TOR.

' AGENT May 10, 1966 e. JENNY 3,250,843

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OSCil/ On .7 fiefl df V r v Q frolyfmlmpregnmed per I d Gear 35 Jenn F09- 5 2 I lNp- To By W9 United States Patent 3,250,843 ELECTRONIC MUSICALINSTRUMENT WITH FLUID PRESSURE ACTUATED VOLUME CONTROL Georges Jenny,Quessigny (Euro), France Filed Aug. 19, 1964, Ser. No. 390,694 8 Claims.(Cl. 841.09)

This application is a continuation-in-part of my application Ser. No.123,818, filed July 13, 1961.

My present invention relates to a musical instrument of the type whereinnotes of dilferent audible 'frequencies are produced with the aid of anelectronic oscillation generator under the control of individuallyoperable tone selectors, such as a set of buttons or keys of a keyboard.

Although the operation and control of such electronic tone generators iswell known per se, it has not yet been possible to operate them in sucha way that their acoustic performance resembles that of conventionalbody-operated musical instruments, particularly wind instruments.

Thus, notes produced by wind instruments (a term here intended toinclude. not only instruments actuated by the mouth of the player, suchas flutes, harmonicas and the like, but also instruments such asaccordions in which the wind is generatedby manual compression andexpansion of a bellows) have a distinct intensity characteristic whichis due to the fact that the medium which excites the individual soundgenerators, e.g. reeds, is an intermittent air stream which varies inintensity, and sometimes (as in a harmonica or accordion) in direction,at a subaudible rate so that there occurs a distinct amplitudemodulation of each note. The general object of my invention is toprovide, in an electronic musical instrument, means for simulating theperformance of such wind instruments,

This object is realized, in accordance with my present invention, by theprovision of a body-actuated source of air flow, such as a mouthpiece ora bellows operable by hand or foot, in combination with flow-backingmeans oscillat-able at subaudible frequencies or otherwise displaceableat a relatively slow rate in response to variations o-r reversals of theair flow, the flow-blocking means electrically controlling anamplitude-modulating network in the output circuit of an associatedelectronic tone generator.

The flowblocking means, positioned, to intercept the air current fromthe mouthpiece or bellows, may be a closed or substantially closedelastic bag, a spring loaded piston, or some other element resilientlyobstructing or impeding the flow. Resilient biasing, however, is notabsolutely essential in the case of a reversible air flow, e.g. asproduced by an accordion, in which, for example, an elastic or inelasticmembrane may be used as the flowblocking and pressure-responsiveelement. Such a membrane, which can be regarded as a double-actingpiston, may also be replaced by a pair of oppositely biased pistonsdisposed side by side and interconnected by a mechanical linkage whichin turn acts upon a variable impedance element constituting part of theamplitude-modulating network. This network may also include otherselectively adjustable impedances, e.g. capacitors, for varying its timeconstant and therefore the response characteristics of the modulator.Mechanical variation of this response characteristic is possible,alternatively or supplementally, with the aid of devices for selectivelythrottling the flow of air into or past the flow-blocking means.

The amplitude of the generator may also be modulated more directly bypassing its oscillating output current through a potentiometer or othervariable impedance element controlled by a device which responds to thepressure of the air flow. I have found, in accordance 3,250,843 PatentedMay 10, 1966 "ice with a further feature of my invention, that aparticularly suitable potentiometer for this purpose comprises a wiperwith a porous body permeated by an electrolytic liquid so that theresistance element of the potentiometer is contacted by liquid filmrather than by a solid conductor, with the result that friction andbacklash are minimized. A very effective electrolytic liquid for thispurpose is a solution of magnesium chloride in a nonvolatile alcohol,preferably glycerol. I

The above and other features of my invention will become more readilyapparent in the following detailed description of certain embodiments,reference being made to the accompanying drawing in which:

FIG. 1 is a partly diagrammatical view of a mouthoperated modulatingsystem according to the invention, as originally disclosed in myabove-mentioned copending application;

FIG. 2 is a cross-sectional view of an accordion embodying the inventionin modified form;

FIG. 3 illustrates, again partly diagrammatically, a furthermodification of the invention as applied to an accordion;

FIG. 4, in still another partly diagrammatical view, illustrates afurther embodiment; and

FIG. 5 diagrammatically shows yet another embodiment.

In FIG. 1 I have illustrated a keyboard whose keys 11 individuallycontrol, in a manner known per so, an oscillation generator 12 via a Setof conductors symbolized by a connection 13. An output lead 14 ofgenerator 12 terminates at the control grid of an amplifier tube 15,here shown as a tetrode, whose plate is connected to a high positivevoltage via a resistor 16 and is further coupled to a loudspeaker 17 byway of a blocking condenser 18 and a filter 19. The screen grid oftetrode is connected via leads 33, 34 to positive voltage at a battery20 by way of a set of variable resistances 21, 22, 23 all connected inparallel, these resistances consisting for example of blocks ofelectrically conductive foam rubber whose conductivity increases as theblocks are compressed. A metal plate 24, pivotally mounted at 25, bearsupon the blocks 21-23 under pressure of an inflatable bag 26 ofresilient material, e.g. rubber, having a mouthpiece 27 into which theuser mayblow. A shunt circuit of manually adjustable impedance,including a first condenser 28 in series with a switch 29 and a secondcondenser 30 in parallel therewith, is connected across thevariable-impedance unit 21-27 to permit selective altering of the timeconstant of the RC network 20-30 connected to the screen grid ofamplifier tube 15.

In operation, a skilled musician will be able to produce a variety ofartistic expressions in modulating the output of tone generator 12, asselected with the aid of keyboard 10, under the control of his ownbreath as he blows more lightly or more strongly into the mouthpiece 27;in the absence of any air pressure applied to the bag 26, the conductiveplate 24 may be disconnected from the resistances 21-23 so that thescreen grid of tube 15 receives negative bias from a battery 31 througha large resistance 32 and the tube 15 is elfectively cut off. Naturally,the resistances 21-23 may also be so arranged that the tube 15 retainssome conductivity in the no-pressure condition whereby a note of minimumintensity can be heard when one of the keys 11 is depressed withoutconcurrent blowing.

In FIG. 2, I have shown at the bellows of an otherwise conventionalaccordion provided with an attachment 41 which forms a passage 42communicating with the interior of the bellows. Passage 42 has a pair oflateral ports 43, 44 in which two pistons 45, 46 are movable in responseto pressure differentials between the interior of the bellows and thesurrounding atmosphere; piston 45 is displaceable when this pressuredifferential is positive, i.e. when the bellows 40 is compressed whereaspiston 46 leaves its normal position when suction is created by anextension of the bellows. The keyboard of the accordion (not shown) isconnected, in the manner illustrated for keyboard of FIG. 1, to anoscillation generator whose output is amplitude-modulated by anamplifier such as the tube of FIG. 1, having an input lead 33, connectedto a conductive bracket 47 carrying a block 48 of variable electricalresistance similar to the blocks 21-23 of FIG. 1. The rods 45', 46' ofpistons 45 and 46 bear upon opposite extremities of a lever 49 whosecenter is fulcrumed to a bar 50 depending from a conductive plate 51which in turn is connected to the conductor 34 leading to a source ofbias voltage as shown in FIG. 1.

It will be apparent that the differential linkage 45', 46, 49-51 in thesystem of FIG. 2 applies pressure to the variable resistance 48 uponboth compression and expansion of the accordion bellows 40, therebymodulating the amplitude of the notes produced by the associated tonegenerator. This instrument, therefore, can be worked essentially in thesame manner as the one shown in FIG. 1, except that the air pressure isnow applied manually rather than by mouth. Naturally, the performance ofthe tone generator may be further controlled by adjustable impedances,e.g. as illustrated at 2830 in FIG. 1.

In FIG. 3, I have shown an accordion bellows 60 having a flexiblemembrane 61 inserted in an end wall thereof. Membrane 61-is conductivelycoated and electrically connected to a source 62 of alternating currentwhose other terminal is connected to a pair of rigid plates 63, 64,spaced from the membrane on opposite sides thereof, via the primarywindings of respective transformers 65, 66. The secondary windings ofthese transformers are connected to the grids of a pair of triodes 67,68 connected in push-pull across a source of operating voltage hereshown as a battery 69, the two grids being biased by another battery 70;tubes 67 and 68 work into an output transformer 71 connected to adetector 72 which applies their rectified output to the lead 33 of theamplitude modulator (not shown in this figure).

In operation, deflection of the membrane 61 in either direction by theoperation of bellows 60 will unbalance the push-pull in connected tubes67, 68 by making the capacitance of one input condenser 61, 63 differentfrom that of the other input condenser 61, 64 so that a control voltagewill appear on the lead 33 in the output of detector 72. The magnitudeof this control voltage will again be determined by the pressuredifferential existing between the interior of the bellows and thesurrounding atmosphere but will be substantially independent of the signof this differential. The bias of battery 70 may also be madesufliciently negative to cut off both tubes 67, 68 until the deflectionof membrane 61 is substantial enough to lower the impedance of eithercondenser 61, 63, or 61, 64 to less than a predetermined cutoff valuewhereby only one or the other of the tubes 67 and 68 will conduct at anytime.

In FIG. 4, I have shown an inlet tube 80 through which a flow of air,originating for example from a mouthpiece as shown at 27 in FIG. 1,enters an enclosure 81 provided with an internal partition 82. On oneside of this partition there is disposed a light source 83 whose raysare directed toward a photoelectric cell 84 on the opposite side of thepartition, the path of the rays being normally cut off by a light gaterepresented by a swingable baflle 85 which is urged under pressure of aspring 86 against the partition 82. The oncoming air stream opens thelight gate to a greater or lesser extent, depending on its intensity, bydeflecting the baffle 85 against the force of its biasing spring 86 sothat the air may escape through an outlet 87; this outlet carries athrottle valve 88 for regulating the flow resistance of the passage 80,81, 87.

Light source 83 is a glow tube energizable by :a battery 89 via a pairof normally open contacts 90 which are closed upon depression of any key11 of the keyboard 10 4 (see FIG. 1), the contacts of all the keys 11being connected in parallel. FIG. 4 also illustrates another set ofcontacts 91 individual to the particular key 11, which connect groundpotential to the associated conductor 13 leading to the oscillationgenerator. Photocell 84 is energized by a battery 92 and has its outputelectrically connected to the control lead 33 of the amplitudemodulator.

In operation, battery 92 applies a control voltage to lead 33 only uponillumination of photocell 84 when the light gate 85 is partly or fullyopened, the magnitude of this voltage thus depending upon the intensityof the air stream flowing through tube 80 and exiting via outlet 87.This air stream is again under direct body control of the operator,Whether produced by blowing, manual compression of a bellows or steppingupon a pedal, so that the acoustic output of the tone generator willreflect the artistic performance of the operator.

In FIG. 5, finally, there is illustrated a potentiometer connected inthe output lead 14 of the oscillation generator 12, this potentiometerincluding a resistance 101 contacted by a wiper 102 on the free end of aconductive spring 103 which in turn is connected to the loudspeaker 17.Spring 103 is acted upon by the bag 26 of FIG. 1 so as to make the wiper102 slide along the resistance element 101 as the bag is inflated byblowing into'the mouthpiece 27. Wiper 102 has a porous body e.g. offelt, permeated by a conductive liquid, preferably a source of magnesiumchloride in glycerol; a proportion of three parts glycerol (by volume)to one part of MgCl has been found extremely suitable. It should benoted that this solution, like any other electrolyte, would tend topolarize it direct current were applied to the potentiometer; with thearrangement illustrated, in which the alternating output of oscillator12 passes through the potentiometer, this is not the case.

The potentiometer 100 shown in FIG. 5 operates substantially withoutinertia and quickly responds to the expansions and contractions of thebag 26 at subaudible frequencies. Naturally, a potentiometer of thiskind could also be used with, for example, a piston type controller ofthe construction shown in FIG. 2 or other control device responsive toair pressure. Other compatible features shown in dilferent embodimentsmay be similarly combined, these and further modifications readilyapparent to persons skilled in the art being intended to be embracedwithin the spirit and scope of my invention as defined in the appendedclaims.

I claim:

1. In a musical instrument having an electronic tone generator providedwith a control circuit, electro-acoustic transducer means connected tothe output of said generator, and a multiplicity of individuallyoperable tone selectors connected to said generator for energizing thelatter to produce electrical oscillations with a variety of audiblefrequencies translatable by said transducer means into sound waves, thecombination therewith of a bodyactuated source of air flow,flow-blocking means displaceable in response to variations of said airflow, and ampli tilde-modulating means for said oscillations controlledby said flow-blocking means, said amplitude-modulating means including apressure-sensitive impedance element of compressible resistance materialconnected in said control circuit and a physical connection from saidflow-blocking means to said element.

2. The combination defined in claim 1 wherein said source comprises amouthpiece.

3. The combination defined in claim 1 wherein said source comprises amanually operable bellows.

4. The combination defined in claim 2 wherein said flow-blocking meanscomprises an inflatable bag.

5. In a musical instrument having an electronic tone generator providedwith a control circuit, electro-acoustic transducer means connected tothe output of said generator, and a multiplicity of individuallyoperable tone selectors connected to said generator for energizing thelatter to produce electrical oscillations with a variety of audiblefrequencies translatable by said transducer means into sound waves, thecombination therewith of a bodyactuated source of reversible air flow,means forming a pair of interconnected passages for said air flow, firstand second flow-blocking means respectively displaceable in saidpassages in response to air flow in either of two directions, andamplitude-modulating means for said oscillations controlled by saidfirst and second flow-blocking means, said amplitude modulating meansincluding a variable impedance element connected in said control circuitand a physical connection from each of said flow-blocking means to saidelement.

6. The combination defined in claim 5 wherein said physical connectioncomprises a differential linkage.

7. The combination defined in claim 5 wherein said impedance elementcomprises a pressure-sensitive body of compressible resistance material.

8. In a musical instrument having an electronic tone generator providedwith a control circuit, electro-acoustic transducer means connected tothe output circuit of said generator, and a multiplicity of individuallyoperable tone selectors connected to said generator for energizing thelatter to produce electrical oscillations with a variety of 10 latingmeans comprising variable impedance means connected in said outputcircuit and physically coupled with said linkage.

References Cited by the Examiner 15 UNITED STATES PATENTS 1,975,22010/1934 Ananiew 841.27 2,301,184 11/1942 Arnold 841.27 X 2,475,1687/1949 Workman 841.01

2Q FOREIGN PATENTS 424,892 2/ 1935 Great Britain.

4 GEORGE N. WESTBY, Primary Examiner.

1. IN A MUSICAL INSTRUMENT HAVING AN ELECTRONIC TONE GENERATOR PROVIDEDWITH A CONTROL CIRCUIT, ELECTRO-ACOUSTIC TRANSDUCER MEANS CONNECTED TOTHE OUTPUT OF SAID GENERATOR, AND A MULTIPLICITY OF INDIVIDUALLYOPERABLE TONE SELECTORS CONNECTED TO SAID GENERATOR FOR ENERGIZING THELATTER TO PRODUCE ELECTRICAL OSCILLATIONS WITH A VARIETY OF AUDIBLEFREQUENCIES TRANSLATABLE BY SAID TRANSDUCER MEANS INTO SOUND WAVES, THECOMBINATION THEREWITH OF A BODYACTUATED SOURCE OF AIR FLOW,FLOW-BLOCKING MEANS DISPLACEABLE IN RESPONSE TO VARIATIONS OF SAID AIRFLOW, AND AMPLITUDE-MODULATING MEANS FOR SAID OSCILALTIONS CONTROLLED BYSAID FLOW-BLOCKING MEANS, SAID AMPLITUDE-MODULATING MEANS INCLUDING APRESSURE-SENSITIVE IMPEDANCE ELEMENT OF COMPRESSIBLE RESISTANCE MATERIALCONNECTED IN SAID CONTROL CIRCUIT AND A PHYSICAL CONNECTION FROM SAIDFLOW-BLOCKING MEANS TO SAID ELEMENT.